Number of consolidated subsidiaries reported by the Company.

No definition available.

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- Definition

Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

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- Definition

The cash outflow associated with the purchase of noncontrolling interest during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

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- Definition

Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Related Party Transactions (Non-Controlling Interests) (Narrative) (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2017 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Distributions to non-controlling interests			$ 22,728	$ 0	$ 0
Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Fair value of contingent consideration (earn-out liability)			102,534	$ 0	$ 0
Management [Member]
Related Party Transaction [Line Items]
Payments for acquisition of non-controlling interests	$ 21,400
Distributions to non-controlling interests			$ 1,300
Management [Member] \| Forecast [Member]
Related Party Transaction [Line Items]
Distributions to non-controlling interests		$ 600
Management [Member] \| Subcontracting Arrangements [Member]
Related Party Transaction [Line Items]
Non-controlling interests, number of subsidiaries,			1
Management [Member] \| Acquisition of Non-Controlling Interest [Member]
Related Party Transaction [Line Items]
Non-controlling interests, number of subsidiaries,	1
Management [Member] \| Acquisition of Non-Controlling Interest [Member] \| Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Fair value of contingent consideration (earn-out liability)	$ 9,000